The present invention relates to a camera with strobe flash illumination for capturing an image of an object, and to a document scanning system and method of using such a camera to capture an image of a document.
In recent years, document scanners have become commonplace. Although these work well and are relatively inexpensive, a document scanner occupies a significant amount of scarce desk space.
The use of a camera to take a photograph of a document consisting of text and/or images offers one way of dealing with the problem of wasted desk space. In conventional film or electronic photography, a person may look through a viewfinder to aim the camera at an object. When the object is a document, for example a document lying on a desk in an office illuminated by ambient light from windows and overhead lighting, it will usually be necessary to use an additional source of light, such as a conventional electronic flash synchronised with a mechanical shutter or electronic capture of the image. Often a person has to stand up, lean over the document, and then take the photograph, in which case, the person's body may block ambient light, thereby requiring the use of a flash even if the ambient light is bright.
Such a flash reduces exposure time and therefore helps to reduce or substantially eliminate camera shake or other relative movement between the camera and an object in an object plane of the camera, particularly when the camera is hand-held. A flash also provides light with a known colour temperature to produce an image that is a true colour. When a photograph is to be taken of an object with a shiny or glossy surface, then ambient light can at certain angles be reflected from the surface and overwhelm the image of the document itself. In this case, a flash can provide sufficient illumination to overcome such stray reflections so that the document can be correctly imaged.
Although conventional flash units are effective in dealing with these problems, a bright flash of light from such a unit can be startling or annoying to anyone nearby. Even if a person is partially shielded directly from such a flash, for example by an office cubical, the eye is very sensitive to any sudden flicker of light. For this reason it is generally considered unacceptable to use conventional flash illumination in many environments, particularly in an office environment, where others could be disturbed by a flash.
Digital camera products are becoming common in many areas of still and motion photography, and as a result are becoming ever less expensive. However such cameras are still used almost exclusively for photography of people or places, and have yet to be adapted for use in office imaging applications. One reason for this is that most electronic cameras, which normally employ two dimensional CCD arrays, have insufficient resolution to image a complete A4 size page at 300 dots per inch, the minimum that is conventionally believed necessary for reasonably high quality reproduction. Whilst higher resolution CCDs are available in electronic cameras, they are much too expensive for a mass-market office imaging product.
As a result cameras with flash attachments and electronic cameras are not widely used in place of document scanners in an office environment.